[Bug rtl-optimization/109035] meaningless memory store on RISC-V and LoongArch

["chenglulu at loongson dot cn" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109035

chenglulu <chenglulu at loongson dot cn> changed:

           What    |Removed                     |Added
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                 CC|                            |chenglulu at loongson dot cn

--- Comment #2 from chenglulu <chenglulu at loongson dot cn> ---
I think this is most likely caused by the implementation of the public code. If
the immediate value is set to be large enough, such as 0xfffffff, aarch64 also
has the same problem.

$ cat t.c
int test(int x)
{
        char buf[0xfffffff];
        return buf[x];
}

$ ./cc1 t.c -o - -O2  2>/dev/null | grep test -A20
test:
.LFB0:
        .cfi_startproc
        mov     x12, 16
        mov     x2, 16
        movk    x12, 0x1000, lsl 16
        sub     sp, sp, x12
        .cfi_def_cfa_offset 268435472
        movk    x2, 0x1000, lsl 16
        mov     x1, -268435456
        add     x1, x2, x1
        add     x1, sp, x1
        str     x1, [sp, 8]
        ldrb    w0, [x1, w0, sxtw]
        add     sp, sp, x12
        .cfi_def_cfa_offset 0
        ret

The "str x1, [sp, 8]" instruction also has the same problem.